U.S. patent number 4,598,871 [Application Number 06/608,882] was granted by the patent office on 1986-07-08 for multiple process electrostatic spray gun having integral power supply.
This patent grant is currently assigned to Nordson Corporation. Invention is credited to Ronald J. Hartle.
United States Patent |
4,598,871 |
Hartle |
July 8, 1986 |
**Please see images for:
( Certificate of Correction ) ** |
Multiple process electrostatic spray gun having integral power
supply
Abstract
An improved electrostatic spray gun wherein the power pack for
transforming a low voltage electrical signal from an external
source to a high voltage signal for application to the gun
electrode is wholly contained within the handle of the gun. The gun
includes multiple interchangeable barrels for enabling the gun to
spray airless atomized liquids, or air spray atomized liquid, or
air-entrained solid particulate materials.
Inventors: |
Hartle; Ronald J. (Lorain,
OH) |
Assignee: |
Nordson Corporation (Amherst,
OH)
|
Family
ID: |
24438457 |
Appl.
No.: |
06/608,882 |
Filed: |
May 10, 1984 |
Current U.S.
Class: |
239/706; 118/629;
239/390 |
Current CPC
Class: |
B05B
5/0531 (20130101) |
Current International
Class: |
B05B
5/053 (20060101); B05B 5/025 (20060101); B05B
005/02 () |
Field of
Search: |
;239/690,691,704-708,390,391,600,525,695,396,526 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Translation of German Specification "Electrostatic Spray Gun"; Roll
No. G 81-19, 946.5; 9-9-1982..
|
Primary Examiner: Peters, Jr.; Joseph F.
Assistant Examiner: Edelbrock; Daniel R.
Attorney, Agent or Firm: Wood, Herron & Evans
Claims
I claim:
1. An electrostatic spray gun comprising:
a handle section, a trigger pivotally mounted upon said handle
section,
a booster power supply contained solely in said handle section,
said booster power supply being operable to convert low voltage
electrical energy supplied to said handle section of said gun into
high voltage electrical energy,
a first barrel section, a flow control valve in said first barrel
section, said first barrel section including an electrode mounted
thereon, said first barrel section including means for removably
securing said first barrel section to said handle section, said
first barrel section having first connector means for electrically
connecting said electrode of said first barrel section to said
booster power supply, and second connector means for connecting
said flow control valve to said trigger of said handle section,
said first barrel section further including means for attaching
said first barrel section to a source of air and to a source of
liquid so as to enable said gun to spray an electrostatically
charged, air atomized liquid therefrom,
a second barrel section, a flow control valve in said second barrel
section, said section barrel section including an electrode mounted
thereon, said second barrel section including means for removably
securing said second barrel section to said handle section, said
second barrel section including first connector means for
electrically connecting said electrode of said second barrel
section to said booster power supply, and second connector means
for connecting said flow control valve of said second barrel
section to said trigger of said handle section, said second barrel
section further including means for attaching said second barrels
section to a source of high pressure liquid so as to enable said
gun to spray an electrostatically charged, airless atomized liquid
therefrom,
a third barrel section, said third barrel section including an
electrode mounted thereon, said third barrel section including
means for removably securing said third barrel section to said
handle section, said third barrel section having connector means
thereon for electrically connecting said electrode of said third
barrel section to said booster power supply in said handle section,
said third barrel section further including means for attaching
said third barrel section to a source of air entrained powder so as
to enable said gun to spray an electrostatically charged air
entrained powder therefrom, and
said first barrel section, second barrel section, and third barrel
section being selectively and alternatively attachable to said
handle section to enable said gun to alternatively spray air
atomized liquid coating material, airless atomized liquid coating
material, and air entrained solid particulate coating material,
respectively.
2. The electrostatic spray gun of claim 1 which further includes
electrical contact means on said handle section and on each of said
first, second and third barrel sections for automatically
establishing electrical contact between said booster power supply
and said electrodes of said first, second and third barrel sections
in response to attachment of said first, second and third barrel
sections to said handle section.
3. An electrostatic spray gun comprising:
a handle section, a trigger pivotally mounted upon said handle
section,
a booster power supply contained solely in said handle section,
said booster power supply being operable to convert low voltage
electrical energy supplied to said handle section of said gun into
high voltage electrical energy,
a first barrel section, a flow control valve in said first barrel
section, said first barrel section including an electrode mounted
thereon, said first barrel section including means for removably
securing said first barrel section to said handle section, said
first barrel section having first connector means for electrically
connecting said electrode of said first barrel section to said
booster power supply, and second connector means for connecting
said flow control valve to said trigger of said handle section,
said first barrel section further including means for attaching
said first barrel section to a source of air and to a source of
liquid so as to enable said gun to spray an electrostatically
charged, air atomized liquid therefrom,
a second barrel section, a flow control valve in said second barrel
section, said second barrel section including an electrode mounted
thereon, said second barrel section including means for removably
securing said second barrel section to said handle section, said
second barrel section including first connector means for
electrically connecting said electrode of said second barrel
section to said booster power supply, and second connector means
for connecting said flow control valve of said second barrel
section to said trigger of said handle section, said second barrel
section further including means for attaching said second barrel
section to a source of high pressure liquid so as to enable said
gun to spray an electrostatically charged, airless atomized liquid
therefrom, and
said first barrel section and second barrel sections being
selectively and alternatively attachable to said handle section to
enable said gun to alternatively spray air atomized liquid coating
material and airless atomized liquid coating material,
respectively.
4. The electrostatic spray gun of claim 3 which further includes
electrical contact means on said handle section and on each of said
first and second barrel sections for automatically establishing
electrical contact between said booster power supply and said
electrodes of said first and second barrel sections in response to
attachment of said first and second barrel sections to said handle
section.
Description
This invention relates to electrostatic spray coating systems, and
more particularly to an improved electrostatic spray gun for use in
such systems.
Electrostatic spray coating systems of the general type to which
this invention relates typically include as a principal component
thereof an electrostatic spray gun. The gun has a handle designed
to be manually grasped by the operator and a barrel which at its
forward end terminates in a nozzle. A spray of coating material,
which may be in the form of an atomized liquid or an air-entrained
solid powder, flows from the gun nozzle toward the object being
coated when an actuator of the handle, such as a trigger, is
actuated by the operator. An electrode, electrically insulated from
the gun handle, trigger, and barrel, is mounted in the nozzle and
is maintained at a high DC potential, e.g., 76 kv, for
electrostatically charging the coating particles as they leave the
nozzle. Electrostatic charging of the particles enhances, for
well-known reasons, the deposition of the coating on the article
being coated, which is typically maintained at ground
potential.
Electrostatic spray systems typically include a power pack or
booster supply for transforming low voltage power to a high DC
voltage which is then applied to the gun electrode for
electrostatically charging the coating particles as they emerge
from the gun. According to the disclosure of U.S. Pat. No.
3,731,145 of Robert S. Senay, this power pack may be contained
wholly within the gun so as to eliminate the need for a heavy high
voltage cable to interconnect the power pack and the gun. According
to the disclosure of this Senay patent, which patent is assigned to
the assignee of this application, the power pack comprises a
transformer which is mounted in the handle section of the gun and a
voltage multiplier contained within the barrel section of the
gun.
One characteristic of all electrostatic spray guns which have
heretofore incorporated a power pack into the gun is that such guns
incorporate a substantial portion of the power pack in the barrel
end of the gun. As so located, the gun is difficult for an operator
to utilize for a long period of time without suffering arm fatigue
as a result of handling that relatively large weight at the end of
the barrel displaced from the handle of the gun.
It has therefore been our objective of this invention to provide an
improved electrostatic spray gun wherein the operator suffers less
fatigue and may maneuver the gun more easily than has heretofore
been possible with guns which have heretofore incorporated the
power pack into the gun.
According to the practice of this aspect of the invention, the
complete power pack of the gun is located within the handle section
of the gun.
Electrostatic spray guns having the power pack contained within the
gun have in the past been used to electrostatically spray air
atomized liquid coating materials as well as airless atomized
liquid coating materials and air-entrained solid particulate
coating materials. Air atomized liquid coating materials are those
which are atomized by impact of an airstream with the liquid
material as it is discharged from the nozzle of the gun. Airless
atomized liquid coating materials are those which are atomized as a
result of being forced through a very small orifice at a very high
pressure. All of these coating materials, i.e., air atomized
liquids, airless atomized liquids, and air-entrained solid
particulate materials, require that they be sprayed from different
electrostatic spray guns, all of which, prior to the invention of
this application, have required different barrel configurations as
well as different handle configurations. The manufacture and
inventory of all of these different varieties of electrostatic
spray guns is very expensive. It has therefore been an objective of
this invention to provide an improved electrostatic spray gun which
is capable of spraying all of these different types of coating
materials with a minimum of different electrostatic spray gun
components. To accomplish that end, the invention of this
application utilizes a common handle and htree different barrels,
each barrel of which is capable of spraying one of an airless
liquid spray or an air atomized liquid spray, or an air-entrained
solid particulate material. By utilizing a common handle for all
three different types of guns, the manufacturing costs and
inventory requirements for the three different types of spray guns
are substantially reduced.
Location of the power pack within the handle section of the gun in
a gun wherein multiple different barrels may be interchangeably
attached to the handle section results in a construction wherein a
user of multiple different guns will need only on handle and power
pack to accomplish spraying of different materials utilizing
different spray processes through differeing barrels. Consequently,
the cost of the barrels is substantially reduced over what would
otherwise be the cost if each barrel contained a portion in all of
the power pack.
These and other objects and advantages of this invention will be
more readily apparent from the following description of the
drawings in which:
FIG. 1 is a side elevational view of a handle and three different
barrels interchangeably usable in combination with the handle in
accordance with the practice of the invention of this
application.
FIG. 2 is a cross-sectional view through the handle and airless
liquid spray barrel of FIG. 1.
FIG. 2a is a cross-sectional view taken on line 2a--2a of FIG.
2.
FIG. 3 is a cross-sectional view through the handle and the powder
spray barrel of FIG. 1.
FIG. 3a is a cross-sectional view taken on line 3a--3a of FIG.
3.
FIG. 4 is a cross-sectional view partially broken away of the
handle and air spray barrel of FIG. 1.
FIG. 5 is a cross-sectional view taken on line 5--5 of FIG. 4.
FIG. 6 is a cross-sectional view taken on line 6--6 of FIG. 5.
FIG. 7 is a cross-sectional view of the electrical power pack
utilized in the handle of the gun according to the practice of this
invention.
FIG. 8 is an electrical circuit diagram of the power pack of FIG.
7.
According to the invention of this application, three different
barrels 10, 11 and 12 are utilized alternatively with a single
common handle 13 to electrostatically spray either liquid or solid
powder coating materials from a gun which combines one of these
barrels with the handle. Specifically, the barrel 10, when utilized
in combination with the handle 13, effects airless atomization of
liquid sprayed from the gun. The barrel 12, when utilized in
combination with handle 13, effects air atomization of liquid
material emitted from the nozzle of the gun. And, the barrel 11,
when utilized in combination with the handle 13, sprays
air-entrained solid particulate powder from the gun. In all
instances, though, the coating material emerging from the composite
gun is electrostatically charged.
Airless Spray Gun
Referring first to FIGS. 1 and 2, the airless liquid atomization
gun is illustrated. As may be seen in these figures, the airless
gun 14 includes the handle 13, designed to be manually grasped by
the operator, and the barrel 10 terminating at its forward end in a
nozzle 15. A spray of finely divided, or atomized, particles of
coating material such as paint, lacquer or the like, flows from the
nozzle 15 toward an object to be coated when the gun trigger 16 is
activated by the operator. An electrode 17, electrically insulated
from the gun handle 13, trigger 16, and barrel 10, is mounted in
the nozzle 15 and maintained at a high DC potential, either
positive or negative, for charging the coating particles in the
spray as the particles leave the nozzle 15. Charging of the coating
particles enhances, for reasons well-known in the art, the
deposition of the coating particles on a target article being
coated which is maintained at an electrical potential different
from that of the electrode 17, such as ground potential.
A source of coating material is connected via a suitable fluid
conduit 18 to the barrel 10 of the gun. A pump (not shown) is
connected in line 18 between the source of coating material and the
gun barrel 10. This pump is operative to pressurize the coating
material so as to facilitate atomization of the coating material by
the nozzle 15 as in conventional in the airless spray
technique.
An electrical powre pack or booster supply 20 is housed within the
gun handle 13 for supplying a high DC voltage, for example 76 kv,
to the electrode 17 from a low voltage DC source 21, for example,
an 11 volt DC supply. The low voltage source 21 is connected to the
gun handle 13 via a low voltage line 22. For convenience, the low
voltage DC source 21 connects via line 23 to a conventional 120
volt, 60 Hz AC source.
The handle 13 preferably is molded of electrically non-conductive
material, such as polyphenylenesulfide, and is provided with an
internal cavity 25 which houses certain of the operating components
of the electrostatic spray gun system, including the electrical
power pack or booster supply 20. The cavity 25 is open at its lower
end 26 to permit introduction of the low voltage line 22 into the
interior of the gun. A palm pad 24 of electrically conductive
plastic is provided in the rear of the handle. The pad 24 is
grounded through a conventional handle grounding circuit so as to
protect an operator against electrical shock.
The voltage booster or power pack 20 is generally cylindrical in
configuration and is configured so as to fit within a bore 27 of
the handl 13. The power pack 20 is potted within the bore 27 so as
to be permanently fixed therein. Except for its configuration so as
to fit within the handle 13, this power pack is known to the prior
art and per se forms no part of the invention of this application.
This application contains a complete description of the power pack
20 only because applicant has been unable to locate a published
English language description of this power pack.
The components of the voltage booster 20 comprise a
transistor-oscillator circuit 28, a transformer 29, and a voltage
multiplier 30 connected one behind the other and arranged as shown
in FIGS. 7 and 8 around a central acetyl resin core 31. In a
preferred embodiment of this core 31, it is made of "Delrin"
plastic.
The voltage multiplier 30 is designed according to FIG. 8 as a
cascade circuit 32 which consists of two rows of capacitors 33
connected in a series and rectifier diode components 34, 35
inserted in each case between the rows with alternating forward
directions. The forward direction of diode components 34 extends
from the first to the second row of capacitors, and the forward
direction of diode components 35 extends in the opposite manner
from the second row to the first row of capacitors. The diode
components 34, 35 are in each case connected in pairs to the
connections of the capacitor rows, i.e., on one row of capacitors,
each pair of diodes is connected to the same capacitor connection,
whereas on the other row of capacitors, the two diodes of each pair
are connected to connections which are adjacent to each other on
either side of one of the capacitors 33 of that row. Capacitors 33
of each row of capacitors are designed as shown in FIG. 7 as
circular components, which are stacked on top of each other to form
self-supporting capacitor columns 36 with the intermediate
insertion of one connecting point in each case for the diode
components 34, 35. The capacitor columns 36 extend in each case
along the central core 31 and are diametrically opposite each other
across this core. The diode components 34, 35 are divided into two
groups of diodes, of which one has the diode component 34 of one
forward direction, while the other diode group has diode components
35 of the other forward direction. On the central core 31 between
the two columns 36 of capacitors 33, there is the one diode group
on one side of the central core 31, while the other diode group is
arranged on the other side of the core, so that the diode groups
are also diametrically opposite each other across the core 31 but
shifted by 90.degree. with respect to the capacitor columns 36. The
connections of the capacitor columns 36 have in each case two ends,
one on each side of the column to which the leads 37 of the
adjacent diode groups in each case are soldered. The diode groups
and the capacitor columns thus form together a tubular assembly
forming a closed periphery in itself, which therefore is relatively
stiff dimensionally, which surrounds concentrically the central
core 31, and which contains on either side of the capacitor columns
36 only the diode components 34 or 35 arranged by forward direction
and orientation. In this way, the voltage multiplier 30 has both a
compact and a clear design, so that it can operate with low losses
and low interference, and can be produced so as to occupy a small
space while providing a high level of performance, which
facilitates its installation in the handle 13 of the gun.
The transformer 29 connected as shown in FIG. 8 to the input of the
voltage multiplier 30 according to FIG. 7 also has a tubular design
and surrounds the central core 31 adjacent to the input end of the
multiplier 30. The transformer 29 accordingly has a tubular ferrite
core 38, on which the feedback winding 39 is wound with uniform
spacings of the turns over most of the length of the core, so that
with the least possible number of turns the most uniform possible
magnetization of the transformer core 38 is obtained, and on which
next to the primary winding 40 the feedback winding 39 for the
operation of the oscillator circuit 28 in FIG. 8 is wound. The
secondary winding 41 of the transformer 29 is formed in the manner
shown in FIG. 7 as a chamber coil 42, which contains a coil element
43 cylindrically surrounding the primary winding 40 and the
feedback winding 39, in the outer periphery of which element
several adjacent annular chambers 44 are provided, in which the
wire windings of the secondary winding are situtated. In this way,
the distributed capacitance of the transformer 29 is kept to a
minimum, so that it can be operated at a higher frequency, and
therefore the capacitors 33 of the voltage multiplier 30 can have a
correspondingly smaller capacitance and therefore a smaller size
with a correspondingly lighter weight.
On the side of the transformer 29 facing away from the voltage
multiplier 30 is the oscillator circuit 28. The oscillator circuit
28 forms a power oscillator in which, as shown in FIG. 8, a
transistor 45 with its collector-emitter branch, is inserted in an
oscillating circuit consisting of the primary winding 40 of the
transformer 29 and an electrolyte capacitor 46 connected in
parallel to it, which is connected by way of the positive and the
negative connections to the external DC source 21. The base of the
transistor 45 is connected to one end of the feedback winding 39,
whose other end is wired by way of a parallel circuit 48 consisting
of a resistor and a capacitor to the positive terminal of the power
source 21, to the negative terminal of which the emitter of the
transistor 45 and the one end of the secondary winding 41 of the
transformer 29 are connected, which is connected by way of a
parallel circuit 49 consisting of a resistor and a capacitor to the
one input of the voltage amplifier 30, to a reference line 50
extending out from it, and to an electric shock safety device 51
shown schematically in FIG. 8 on the gun handle to ground it.
A current-limiting resistor 52 is also included in the power pack
20 and is located between the high voltage output of the voltage
multiplier 30 and the power pack output lead 55. This
current-limiting resistor 52 is in the form of a resistor chain 53
consisting of several resistor components 54 connected in series
which are wound around the core 31 between the output end of the
voltage multiplier 30 and the lead 55 to the resistor 56 contained
in the barrel of the gun. The resistor chain 53, the voltage
amplifier 30, the transformer 29, and the oscillator circuit 28 are
cast in resin 57 in the space between the core 31 and a jacket tube
58, this resin having in addition to satisfactory electrical
insulating properties the greatest possible thermal conductivity
for removing the heat generated during the operation of the high
voltage generator. The fastening bracket 59 on which, in addition
to the components of the oscillator circuit 28, the components of
the parallel circuit 49 in FIG. 8 are also arranged, consists of a
metal with good thermal conductivity and is in thermally conductive
contact with a metal tube 60 which is attached to the end of the
central core 31. The fastening bracket 59 and the metal tube 60
thus form a heat-removing component which serves to conduct away
the heat generated in the high voltage generator to the gun
handle.
A microswitch 62 is inserted in the line 22a leading to the
positive terminal of the external DC power source 21; this switch
is housed in a bore 63 of the handle and is actuated by a plunger
61 associated with the trigger of the gun handle. The plunger 61 is
spring biased to an open position of the switch 62 as in
conventional in electrostatic spray guns.
The power pack shown in FIGS. 7 and 8 thus forms an electrostatic
accessory unit which, due to the design of the high voltage
generator housed within it, can be coupled comparatively easily and
manageably to the electrode of an electrostatic spray gun and may
be easily mounted within the handle of the gun.
In a preferred embodiment, the external DC source 21 is designed in
the form of a line device for a voltage of 12 V; the oscillator 28
is designed for a frequency of 20 kHz with an output voltage of 10
kV.sub.ss, whereas the voltage multiplier 30 has twelve stages and
a negative high voltage of 90 kv with an output power of 3.6 W. The
current-limiting resistor 52 inserted between the output of the
voltage multiplier 30 and the output lead 55 has a total resistance
of about 100 megohms, so that the current is limited to 1 megohm.
The maximum thermal conductivity of the casting resin 57 and/or of
the supply tube 60 for improving the removal of the heat generated
in the high voltage generator can be achieved in particular by the
incorporation of a filler with high thermal conductivity such as
quartz flour, kaolin, or mica.
The barrel 10, which is detachably mounted to the handle section 13
of the gun by conventional threaded connectors or bolts (not
shown), preferably is fabricated in two pieces; a metal extrusion
head 19, and a plastic barrel section 19a of a tough, electrically
insulative material. The barrel is made in two pieces so as to
enable the high pressure fittings of hose 18 to be connected to the
metal extension head 19. The two piece barrel 10 is provided with a
first cavity 64 adapted to accommodate a primary electrical
resistor 65. This resistor 65 is connected at one end via a
conventional spring and washer connection 66, a lead 67, and a
small secondary resistor 88 to the electrode 17. At its opposite
end, the primary resistor 65 is removably connected by a spring 89
and cable 55 to the power pack 20. To this end, the cable or lead
55 extends from the handle 13 and is adapted to be received within
the bore 64 of the barrel 10. A contact 70 of resistor 65 is
maintained in electrical conctact with the end 68 of the cable 55
by the spring 89. A dielectric sleeve 64a surrounds the resistor 65
and cable 55 within the bore 64. A second cavity 71 is also
provided in barrel 10. This cavity constitutes a coating flow
passage interconnecting the conduit 18 and the atomizing nozzle 15.
Cavity 71 additionally houses a longitudinally reciprocable
actuating rod 72 which responds to the trigger 16 for opening and
closing a flow valve 73 comprising seat 74 and ball 75. Valve 73
regulates the flow of coating material from the cavity 71 to the
atomizing nozzle 15.
The atomizing nozzle 15 includes a conventional orifice assembly 76
preferably constructed of a metal member 77 having a carbide insert
78 in which an orifice (not shown) is acutally formed. Member 77 is
secured to a generally ring-shaped mounting structure 79 of
insulative material. The orifice-mounting ring 79 is maintained in
operative position relative to the coating flow passage 71 by an
insulative retaining ring 80 which is threaded to the front of the
barrel 10.
The electrode 17 is preferably configured in the form of a needle,
the inner end of which is in electrical contact with the output
terminal of the resistor 55 via an electrical conductor 67.
The trigger 16 is suitably pivotally connected at its upper end to
to the gun handle 13 as shown at 81 for movement between an outer
inactive position shown in solid in FIG. 2 and an inner active
position shown in phantom at 16'. The trigger is biased to the
inactive position by a spring 47. When the trigger is moved to the
active position 16', a rear surface 82 of the trigger contacts the
plunger 61 and actuates a microswitch 62 to energize the power pack
20. In addition to actuating the switch 62 when the trigger 16 is
moved to its active position 16', movement of the trigger also
opens the flow valve 73 to permit the flow of pressurized coating
material from the line 18 through the passage 71 to the orifice
assembly 76 whereat energization takes place. Specifically,
movement of the trigger 16 to its active position 16' rearwardly
reciprocates a guide 83 on the end of an extension 84 of rod 72.
The rod extension 84 slides in an axial bore formed in a seal
member 85, moves the rod 72 rearwardly, in turn unseating the ball
75 from seat 74 to open the flow valve 73. A comprsssion coil
spring 86 sandwiched between the seal member 85 and the circular
shoulder 87 formed on the rod 72 biases the rod 72 and hence the
ball valve 74 to a closed position.
The sequencing of the switch 62 and the valve 73 is such that the
switch 62 closes either simultaneously with of just immediately
prior to the opening of the valve 73. Consequently, any liquid
emitted from the orifice assembly 76 is atomized in the course of
passage from the nozzle and is electrostatically charged as a
result of passing through the elecrostatic field created by the
electrode 17.
The airless spray gun 14 created by the barrel 10 and handle 13 is
operable to atomize liquid supplied from a high pressure source to
the conduit 18 in the same manner as prior art airless spray guns.
The gun 14 differs from conventional prior art airless spray guns
such as that disclosed in U.S. Pat. No. 3,731,145 principally in
that the complete power pack is contained in the handle 13 of the
gun and in that the handle and barrel 10 are so configured as to be
separable and detachable so as to enable other barrels to be
interchanged for the barrel 10 as best illustrated in FIG. 1.
Powder Spray Gun
Referring now to FIG. 3, the same handle 13 is illustrated as
applied to a powder spray barrel 11. With this combination of
powder spray barrel 11 and electrostatic power pack containing
handle 13, the resulting gun 90 may be used to spray air-entrained
solid particulate powder material. Since the complete handle 13 of
a powder spray gun 80 is identical to the handle 13 utilized in the
airless spray gun 14, the components of the handle 13 in the gun 80
have been given identical numeral designations in this gun 90 as in
the gun 14.
The gun 90 is an air-operated electrostatic powder spray gun which
employs the impact of a pressured airstream with a stream of
fluidized coating material to effect spraying of the solid
particulate powder material and formation of the material into a
desired conical spray pattern. The gun comprises the power pack
containing handle 13 and an electrically insulative barrel assembly
11 with an electrically insulative nozzle assembly 91 at the
forward end of the barrel 11. Powder coating material is supplied
to the gun under pressure from an external reservoir or tank
through a hose 92. The hose 92 is adapted to connect it to a
fitting 93 mounted in an opening 94 through the wall of the barrel
11 of the gun. The powder coating material is fluidized by a
pressurized gas such as air and is conveyed through the hose 92 to
the gun under pressure. The barrel 11 includes a second opening 95
extending through the wall thereof in which there is mounted a
fitting 96 through which an air hose 97 with pressurized air is
adapted to be attached.
The nozzle assembly 91 includes a tubular support member 98 formed
of an electrically insulative material. The support tube 98 is
supported at its rearward end 99 in the barrel 11 of the gun 90 and
has at its front end a small diameter portion 100, a larger
diameter portion 101 and a small diameter forwardmost portion 102
all extending forwardly of the rearward end 99. The rearward end 99
includes an internal cavity 103 and an opening 104 extends down the
center of the forwardly-extending portions 100, 101, 102, the axis
of which lies on the center axis of the barrel 11. A resistor 105
slides into the tubular cavity 103 in the rear end 99 of the tube
98, and a charging electrode 106 extends through the opening 104
and out of the forwardmost end 102.
A tubular sleeve 107 slides on the small diameter portion 100 of
the tube 98 and is supported thereby. As may be seen by referring
to FIG. 3A, the section 100 of the support tube 98 is provided with
a pair of flats 108 on two sides thereof to permit the flow of
pressurized air along the sleeve 107 through a passageway 109
defined by the sleeve and the flattened portions 108 and the larger
diameter portion 101 of the support tube 98. As may be seen, this
passageway extends along the center of the barrel and nozzle
assembly and terminates at an open forward end 110 in the form of
an annular gas flow passage 111. The sleeve 107 slides into the
barrel at its rearward end, and an O-ring seal is provided between
the outer surface of the sleeve 107 and the barrel 11 to prevent
leakage of pressurized air entering the barrel 11 through the
opening 95 in the wall thereof along the outside of the sleeve. In
this manner, pressurized air entering the barrel through the
opening 95 is directed through the passageway 109 and out the open
end 110 to the sleeve 107 in thr form of an annular stream of gas
under pressure.
A nozzle 112 is mounted in the forward open end of the barrel 11.
This nozzle includes a central through opening 113 through which
the forward end 110 of the sleeve 107 passes. The inner surface of
the nozzle 112 defines with the outer surface of the sleeve 107, an
annular passageway 114 through which fluidized powder coating
material entering the nozzle assembly 1 through the opening 94 in
the wall of the barrel is emitted from the nozzle. The powder
coating material is emitted from the nozzle 58 in the form of an
annular flow of material encircling the pressurized air flowing out
passageway 111 at the center of the nozzle assembly.
A gas deflector cap 115 is mounted on the forwardmost end 102 of
the support tube 98 and is displaced slightly forwardly of the
forward open end 110 of the sleeve 107. The deflector cap includes
a surface 116 against which the annular stream of pressurized air
issuing out of the open end 110 of the sleeve 107 impacts. The
deflecting surface 116 changes the direction of this stream of
flowing air from one being axially directed along the center of the
nozzle assembly to one which is radially directed outwardly in a
360.degree. pattern. The pressurized air enters the gun through the
opening 95 in the wall of the barrel 11 and is directed through the
passageway 109 and out the annular opening 111 in the open end 110
of the sleeve 107. The pressurized air issuing out of the open end
110 impacts the surface 116 of the deflector cap 115 and is thereby
turned 90.degree. to a radial outward direction. The coating
material enters the nozzle assembly through the openign 94 in the
wall of the barrel 11 and flows along the outside of the sleeve 107
and out the annular opening 114. When the coating material which is
being conveyed by air under pressure is emitted from the nozzle
112, it is impacted by the outwardly-flowing stream of pressurized
air ans is thereby caused to be finely atomized and a uniform,
conical pattern of material results from the impact of the radially
outwardly-flowing stream of air and the axially flowing stream of
powder. The nozzle 112 includes a generally conical surface 117 for
directing the outwardly and forwardly-moving conical spray of
material. The atomized powder is electrically charged by the
electrode 106 extending out of the nozzle assembly 91 and past the
air deflector cap 115.
A spring 118 is sandwiched between resistor 105 and a contact 68 on
the end of the cable 55. This spring maintains electrical contact
between the cable 55 of the handle and the resistor 105 contained
in the barrel 11. A dielectric sleeve 119 encloses the resistor
105, cable 55 and their contacts.
In the operation of the gun 90, the handle is triggered rearwardly
by an operator of the gun so as to close the switch 62. Closing of
this switch is operative to cause low voltage DC power to be
connected to the power pack 20 so as to charge the electrode 106.
Simultaneously, this switch is operative through appropriate
controls to open the powder hose 92 and air hoses 97 to their
respectively supply sources so as to result in powder being
supplied to opening 94 and air under pressure being supplied to the
opening 95.
The powder spray gun 90 is generally conventional in operation
except that the complete power pack of the gun is contained in the
handle 13 and the barrel 11 of the gun is detachably connected
thereto so that it may be removed and interchanged with the barrels
10 and 12. In all other respects, the powder spray gun 80 is
substantially identical to conventional powder spray guns, such as
the gun disclosed in Hollstein U.S. Pat. No. 4,380,320, assigned to
the assignee of this application.
Air Atomizing Gun
With reference now to FIGS. 4, 5 and 6, there is illustrated the
handle 13 in combination with the air atomizing liquid spray gun
barrel 12. This gun 120 relies upon the impact of an airstream with
the liquid stream to effect atomization of the liquid stream.
The gun 120 comprises the previously described handle 13 and an
electrically insulative barrel assembly 12. Paint or liquid spray
coating material is sprayed from the gun under pressure from an
external source (not shown) supplied to the gun via a hydraulic
hose 121.
The hose 121 is connected to an inlet passage 122 in the bottom of
the barrel 12. The inlet passage 122 communicates with an annular
axial fluid flow passageway 123 in the barrel 12. The passageway
123 in turn communicates at its forward end with a central annular
axial passage 124 in the nozzle assembly 125. The passages 123, 124
are substantially axially aligned.
An air hose 126 is connected to an air passage 127 and communicates
through an air flow passage 128 of the barrel with an air valve 129
located within the interior of the barrel. Specifically, the valve
129 is mounted within a large continuation 130 of the passage 123.
This valve 129 is operative to control the flow of atomizing air
via passage 131 to the nozzle assembly 125 and the flow of
fan-shaping pattern or so-called "horn air" to the nozzle 125 via
an internal flow passage 132. The flow passage 132 contains a
needle valve 133 for controlling the quantity of fan-shaping air
supplied to the nozzle assembly upon opening of the air control
valve 129.
The nozzle assembly is made of an electrically non-conductive
material. The nozzle 125 has a fluid tip 134 which is threaded at
its rear into a counterbore in the forward end of the barrel 12.
The fluid tip 134 has a number of circumferentially-spaced axial
passages 135 which open at their rear into the counterbore to
communicate with an annular air passage 136 such that atomizing air
passing through the passage 151 into the passage 136 may enter and
pass through the axial passages 135 in the fluid tip and into an
internal chamber 137 surrounding the forward end of the fluid tip.
The fluid tip also includes the central axial passage 124
communicating with the material flow passageway 123 in the barrel
portion of the gun for supply of paint via the hose 121 from the
tank or reservoir.
The forward end of the fluid tip 134 terminates in a nozzle 139
having a small diameter orifice 141 through which the coating
material is emitted. The fluid tip 134 further includes a coned
seat 142 formed inside the nozzle 139 close to the discharge
orifice 141.
An air cap 143 surrounds the forward end of the fluid tip 134. The
air cap is mounted to the gun by means of an annular retaining ring
148 which is thread over a threaded section of the barrel 12 at one
end and at its other end there is an annular lip 145. The retaining
ring 148, although rigid, is sufficiently flexible at the lip 145
to permit the air cap to be snappd into position with the lip 145
engaging a wall 146 in an annular groove 147 in the outside surface
of the air cap 143 such that the air cap is securely retained and
sealed against the escape of air to the atmosphere.
Flow of the atomizing air is through the openings 150 close to the
nozzle 139, and flow of the fan-shaping air is through openings 151
in the opposed air horns 156.
The flow of paint through the axial flow passageways 123 and 124 is
controlled by a control rod 153. the control rod is mounted at its
rear in the valve assembly 129, the rod being sealed by packing 154
and a flexible bellows seal 155 such that the control rod 153 is
axially slidable in a forward and rearward direction upon operation
of the trigger 16.
The control rod 153 terminates at its forward end in a cone-shaped
tip 156. The coned tip cooperates with the internal seat 142 in the
fluid nozzle 139 to form a needle and seat valve assembly
actuatable by the trigger 16. That is, when the trigger 16 is
pulled rearwardly, the rod 153 is retracted which retracts the
cone-shaped tip 156 of the rod from the valve seat 142 immediately
behind the material discharge orifice 141 allowing the pain in the
passageway 124 to flow around the tip 156 and out the discharge
orifice 141. When the trigger is released, a spring 157 in valve
129 moves the contol rod 153 forwardly with the tip engaging the
valve seat to thereby stop the flow of paint.
A resistor 160 is mounted in the barrel 12 of the gun between a
first spring 161 and a second spring 162 which acts as a contactor
with the contact 68 on the end of the cable 55 extending from the
handle 13. Alternatively, resistor 160 could be integrally mounted
at the end of cable 55, with spring 162 extending from the resistor
160 to make electrical contact with lead 167, and with spring 161
being eliminated in this embodiment. This alternative embodiment
could be used with extensions 10 and 11 as well. The resistor 160
is thus in series with the electrical power pack 20 contained in
the handle 13 of the gun. Within the forward end of the control rod
153 is a second resistor 163. The forward end of the resistor 163
is electrically connected to a thin, stainless steel wire electrode
164 extending through the discharge orifice 141 of the fluid nozzle
139. This electrode 164 ionizes the atomized paint emitted from the
nozzle assembly 125.
The rear end of the resistor 163 is in contct with the metallic pin
165 passing through the rod 153. The pin 165 in turn is in contact
with the conical spring 166 contacting an electrical lead 167. This
lead 167 is connected via spring 161 to resistor 160 and hence the
power pack 20, as described above.
Accordingly, the conical spring 166 and pin 165 cooperate to form
means electrically connecting the conductor 167 with the resistor
163 while permitting axial sliding movement of the actuating rod
153 to open and close the vlave. The path of high voltage
electrical energy from the resistor 160 is thus through the
electrical lead 167, the conical spring 166, the pin 165, and the
resistor 163 to the ionizing electrode 164. The resistor 163 thus
lies in series in the high energy electrical path and lies
forwardly or "downstream" of all the conductive components of the
gun other than the ionizing electrode 164.
The air valve 129 controls not only the supply of atomizd air and
fan-shaping pattern air to the nozzle 125, but also controls the
sequencing of that air supply with the liquid supply to the nozzle
assembly. Specifically, this air control valve 129 is operative to
first open air valve 170 contained internally of the valve 129 and
then after atomizing air and fan-shaping air are being supplied to
the nozzle assembly 125, to then permit the opening of the liquid
valve 171 so that liquid is ejected from the nozzle assembly.
The air valve 129 comprises a valve body 172 through which there
passes a four-piece air valve stem 173. This valve stem 173
comprises an end section 174, a screw section 175, a valve section
176, and an actuation section 177. The end section 174 is
threadedly connected to the stem 153 of the liquid flow control
valve and is sealingly separated therefrom by an end section 178
and packing 154 of the valve body.
The screw section 175 of the valve stem is threaded into the end
section 164 of the stem 173 and slidingly passes through a bore 178
of the valve section 176. The threaded screw section 175 terminates
in a slotted head 179 which acts as a stop to limit the travel of
the valve section 178 relative to the screw section 175. The valve
section is in turn provided with an axial bore into which the
atuating section 177 of the valve stem is threaded. There is a
spring 157 contained internally of the valve for biasing the end
section 174 and thus the attached valve stem 153 of the liquid flow
control valve 171 to a closed position. There is also a second
spring 180 contained internally of th air valve for biasing the air
valve 170 to a closed position relative to its seat 181.
The end 182 of th air valve actuating stem 177 is threaded and has
a threaded collar 183 mounted thereon. This collar 183 is adapted
to be engaged by surface 82 of the trigger 16 so that upon rearward
movement of the trigger about the pivot 81, the actuating section
177 of the air valve 170 will be pulled rearwardly. This results in
opening of the air valve 170 so that high pressure air contained in
the passage 128 may flow through ports 184 in the valve body 172 to
the internal flow chamber 185 of the valve body. This high pressure
air then flows from chamber 185 through valve 170 and via ports 187
to the air atomizing passage 131 and needle valve 133 to the air
fan-shaping passage 132. After the air valve 170 has moved
rearwardly a predetermined and adjustable distance, a shoulder 188
of the valve section 176 engages the slotted head 179 at the end of
the adjustment screw section 175 of the valve stem so that
continued movement of the trigger 16 results in axial movement of
the valve stem 153 and thus the liquid control valve 171. Upon
opening of the liquid control valve, liquid is emitted from gun.
Since the air flow valve 170 had been open prior to opening the
liquid flow control valve 171, liquid emerging from the nozzle of
the gun is impacted by atomized air from the chamber 137 and
fan-shaping pattern air from the horn passages 151 of the nozzle
assembly 125.
In the course of the trigger 16 moving rearwardly, the switch 62
contained in the handle section 13 of the gun 120 is actuated. As
in the previous embodiments, this switch is operative through
appropriate controls to cause high voltage electrical power to be
supplied from the power pack 20 to the electrode 164 of the gun. As
a consequence of this electrode being energized, liquid emerging
from the gun is charged with an electrical charge from the
electrode.
The primary advantage of the multiple guns described hereinabove is
that they all utilize a common novel handle wherein the complete
electrical power pack is controlled. All three guns utilize
interchangeable barrels. As a consequence, the manufacturer of such
guns may substantially reduce its inventory by having only a single
handle assembly for all three different styles of guns or,
alternatively, a customer for such guns may substantially reduce
his equipment costs by being able to utilize a single handle with
three different interchangeable barrels, each of which is capable
of spraying differing materials and generating different spray
patterns.
While I have described only one preferred embodiment of my
invention, persons skilled in this art will appreciate the numerous
changes and modifications which may be made without departing from
the spirit of my invention. Therefore, I do not intend to be
limited except by the scope of the following appended claims.
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